This invention relates to a barrel type vapor-phase growing apparatus wherein semiconductor layers and the like are simultaneously grown on a large number of substrates, and the temperatue distribution in the apparatus can be substantially improved.
Barrel type vapor-phase growing apparatus utilizing radio-frequency heating have been disclosed, for instance, in U.S. Pat. Nos.: 3,424,629; 3,645,230; and 4,496,828.
The apparatus disclosed in the U.S. Pat. No. 3,424,629 utilizes a radio-frequency heating coil wound on the outside of a susceptor. The apparatus of this patent involves difficulties that the distance between the susceptor and the heating coil cannot be reduced and that infrared-ray lamps and the like cannot be provided outside of the susceptor.
In the apparatus disclosed in U.S. Pat. No. 3,645,230, the RF coil is provided on the inside of the susceptor of a cylindrical configuration and opening upwardly and downwardly, and having a lower end supported by a supporting member. This type of growing apparatus involves difficulties that the construction of the supporting member becomes complicated because the susceptor must be rotated while preventing the leakage of reaction gas from a reaction chamber.
On the other hand, in a barrel type vapor-phase growing apparatus disclosed in U.S. Pat. No. 4,496,828, a susceptor having a top plate and a slide plate is suspended by a shaft depending from an upper position.
In still another conventional apparatus shown in FIG. 1, a susceptor 1 of a truncated polygonal cone shape and having a top plate 2 is suspended by a hanger 3, and a radio-frequency heating coil 4 is provided internally of the susceptor 1.
As a consequence, when the susceptor 1 is heated by the heating coil 4, since the top plate 2 is provided at the top of the susceptor 1, the upper end of the heating coil 4 is brought into a position lower than the upper end of the susceptor 1. Thus the temperature at the upper end portion of the susceptor 1 is reduced as indicated by T1 in FIG. 2 because of the heat dissipation toward the top plate 2, and a temperature gradient of a comparatively wide range starting from the upper end of the susceptor has been exhibited at the upper end of the susceptor 1.
The temperature gradient inevitably restricts the mounting area of wafers W, thus reducing the productivity of the growing apparatus. Furthermore, since the upper end portion of the susceptor 1 is ordinarily cooled by a reaction gas and a purging gas, it is advantageous to heat the end portion to a temperature higher than the intermediate portion for avoiding further increase of the temperature drooping region.